1. Field of the Invention
The present invention is directed to a formaldehyde-free method for treating wood products, especially green lumber, to strengthen the wood products and to render the wood products flame retardant and resistant to moisture and insects.
2. Description of the Related Art
Prior art publications disclose treatment of wood products with chemicals such as silicates, creosote, copper naphthenate, pentachlorophenol and chromated copper arsenate to preserve the wood products and to render them fire-retardant and insect repellant. After treatment, the wood products can be painted, soaked or pressure treated to coat and/or impregnate the wood products.
U.S. Pat. No. 3,974,318 to Lilla, discloses such a process. In the Lilla patent, a water soluble silicate composition is applied to a wood product and the product is subsequently treated with a water soluble metallic salt compound to form a water insoluble metallic silicate in the wood product.
Although the prior art methods and compositions are suitable for treating dried lumber and manufactured (engineered) wood products, no products or methods have been found suitable for treating green lumber or other wood products having a high water content.
It is, therefore, an object of the present invention to provide a wood product treatment method and a compound suitable for treatment of wood products, and for treating green lumber as well as to provide a superior method and composition for completely treating dried lumber and manufactured wood products.
The present invention is directed to a method and a composition for treating wood produces and a treated wood product prepared according to the methods of the present invention. The method provides for treating the wood products with a silicate based solution that will fully penetrate and preserve wood products, including green lumber. The method includes pressure treating the wood products in an aqueous solution of sodium silicate which further includes a wetting agent and a rheology modifier at a pH of at least 9.0 and, preferably, at a pH of at least 13.0. Most preferably, the aqueous solution includes a borax and/or a bacteriocide or fungicide. Addition of the rheology modifier and the wetting agent to the solution allows the chemicals to fully penetrate the wood product irrespective of whether the wood product is green lumber or a dried and/or engineered wood product.
The pressure treating method of the present invention includes the following steps: placing the material in a pressure vessel and applying a vacuum; contacting the material with an aqueous solution and increasing the pressure in the pressure vessel; draining the aqueous solution and reducing the pressure, preferably, applying a vacuum; and drying the treated wood product.
In an alternative method, wood particles are mixed in a slurry of the aqueous solution and a glue; the slurry is injected into a press, for instance a steam press, and the slurry is pressed to form a board or other engineered wood product. The engineered wood product can be fiberboard, particle board or oriented strand board. The wood product is then cured. As a further alternative, the aqueous solution and/or other additives can be injected directly into the press prior to pressing and curing.
The composition of the present invention is an aqueous solution having a pH of at least 9.0, preferably of 10-14 and, most preferably, 13.0 and includes silicate, a wetting agent and a rheology modifier, the solution preferably includes borax and/or a bacteriocide or fungicide.
Lastly, the present invention is also directed to pressure treated wood product prepared by one of the above-described methods.